As one of techniques to increase communication capacity in the next-generation communication, a broadband in a super high frequency region may be used for data transmission and reception. However, since the super high frequency region has a great path loss, it is required to improve a beamforming gain by using a plurality of antennas at a terminal and a base station. In this case, since a beam has directivity, the base station and the terminal adjust a beam in a specific direction for communication.
Currently in the cellular network using a frequency region of 5 GHz or less, there is a radio shadow area where a signal of the base station fails to arrive. In order to solve this, a repeater is installed in the radio shadow area. Such a repeater amplifies the signal received from the base station and retransmits it to the terminal. In the 30 GHz millimeter wave (mmWave) region, the repeater is needed essentially because a propagation distance of the signal transmitted from the base station becomes shorter due to a great path loss.
In order to provide a service to users located in a building, an optical repeater may be installed. The base station and the optical repeater are connected by an optical cable. The optical repeater amplifies a signal received from the base station and then sends it to the users in the building. The optical repeater does not perform a beam sweeping. Namely, when the base station sends a signal through each beam, the optical repeater resends the signal by using one or more fixed beams.
In this environment, a channel status between the optical repeater and the terminal does not vary according to beams of the base station. Namely, the channel status is nearly unvaried in case of all beams operated by the base station. Therefore, required is a system operation method optimized for the terminal in such environments.